First of all, the couple has to contact the "Ufficio Comunicazione e Eventi istituzionali" to fix the date and time of marriage:

Ufficio Comunicazione e Eventi istituzionali
P.zza del Popolo, 1 Castelfiorentino
Fax:0571 686387 i.dainelli@comune.castelfiorentino.fi.it  

You will then issue a copy of the documents listed below at least 20 days before the marriage, to the following address:

Ufficio Stato Civile
P.zza del Popolo, 1 Castelfiorentino (FI) 50051 Italy, even by telefax 0571 629355 or enclosed to a message by email

Documents required:

1) Nulla-osta to civil marriage issued in accordance with art. 116, d.c. by the foreign consulate in Italy regularly translated in Italian. This document must contain the exact indication of the name, surname, date and place of birth, residence, citizenship and civil status of the married couple (if the bride is widowed or divorced also the date of the event), the name of their parents and also the name, surname, date and place of birth, residence of the 2 witnesses at the wedding.
2) Copies of your personal identity documents.

A Wedding declaration is also required before the marriage to be drawn up at the Office- Ufficio Stato Civile, P.zza del Popolo, 1 in Castelfiorentino, even few hours before the ceremony. Office Hours: from Tuesday to Saturday 9.00 am-1.00 pm. On Tuesday even 4.00pm-6.00pm.
On this occasion both bride and bridegroom must be present, with an interpreter if necessary, and everyone must haveh his identity document and the original nulla-osta mentioned above.
The office will issue a marriage certificate to allow to get married in Castelfiorentino.

If the the bride and/or the bridegroom are resident the banns are required, applying to the office-Ufficio Stato Civile.Banns should be drawn up in the presence of the both and notice at the Town for four consecutive days.

To have the civil wedding ceremony in  Castello di  Oliveto, Relais Pugliano or Castello di Coiano, you have to fill the form attached ("Richiesta prenotazione sala in Villa storica per la celebrazione di matrimonio civile") and make a deposit on postal giro account number. 25620501, in favour of Comune di Castelfiorentino - Servizio di Tesoreria - with the following description of payment: "Matrimonio in Villa"(Civil wedding at...)
The deposit receipt will be sent to the office -Ufficio Comunicazione e Eventi istituzionali, via email to i.dainelli@comune.castelfiorentino.fi.it .
This deposit receipt will be the confirmation of your marriage.

Enc.:
Form "Richiesta di prenotazione sala in Villa storica per celebrazione di matrimonio civile"
Price list
Regulation for the civil wedding ceremony